To test the function or to calibrate gas sensors, the gas to be measured or a substitute gas that appears to be suitable is admitted, in general, to the gas sensors at fixed time intervals. Either test gas in pressurized gas containers may be used for this together with suitable gas admission means, for example, with pressure reducers, or the test gas may be generated directly and applied to the sensor by means of suitable gas admission devices. The use of pressurized containers with corresponding means is complicated and requires corresponding logistics and handling. To make matters worse, especially in case of the calibration of detectors for combustible gases in the explosive range, potentially explosive gas mixtures must be handled within explosion-proof areas.
It is therefore advantageous for testing the function of sensors for combustible and explosive gases, e.g., of pellistors or IR sensors, to generate the test gas in a quantity sufficient for the testing in the immediate vicinity of the sensor. For example, the release of gas by heating suitable storage materials (US 2005 0 262 924) may be used for this, but this release necessitates an additional heating element, which represents an additional source of hazard in an explosion-proof area. By contrast, electrochemical gas generators offer the intrinsic advantage of inherent safety. When using electrochemical gas generators, it seams most feasible to switch over to a substitute gas calibration with hydrogen (H2), because this gas can be obtained in a simple manner by the electrolysis of protic electrolytes. However, one drawback of this process is that it is not possible to obtain direct information on the sensitivity of the gas sensor to be tested to the primary analyte because the reaction of H2 can be very successful on a partially poisoned catalytic material of a corresponding gas sensor, which is not longer suitable for the measurement of combustible hydrocarbons, e.g. alkanes or alkenes, i.e., the calibration is insufficient and erroneous.